installing small wood stove in an RV.. help!?

[dkl777]

hi folks. this is my first post but I've been lurking for a couple weeks.
I expect to get some "don't do it" replies, but I have a dilemma I'm hoping someone will have some suggestions for.

I have a vintage Airstream type aluminum trailer (Streamline), and I just bought a used Dickinson Marine Newport solid fuel heater for it. http://www.go2marine.com/product/20010F/dickinson-marine-newport-solid-fuel-heater-00-newsf.html
This little stove uses 3 inch stainless pipe, which is also from Dickinson.

Now the problem. Someone used a wood stove in the trailer many years ago, and there is still a piece of 6 inch single wall pipe sticking through the roof. theres flashing on top and a little rain cap and its watertight, but the hole they made is approx 7.5 inches.
Dickinson sells a handy little deck fitting to go through the roof, but the diameter is only 5 inches, and it will not work with the existing hole. The marine stove industry has plenty of fittings for this, but so far they all seem to be too small.

I am now trying to figure out a sensible way to take the 3" pipe through the 7.5" hole, and keep it watertight and safe.
I've thought about a silicone boot, or a 3" pellet stove thimble, or just running the smaller pipe right up through the larger one and packing the sides with something and hoping for the best... basically drilling 5" hole for a factory recommended install is my absolute last resort.

any ideas??
Also, the trailer is permanently parked, so this will NOT be rolling down the road!!

 

[begreen]

You are thinking on the right path. Be sure to mount the stove securely and provide it with a nearby fresh air supply.

 

[dkl777]

I just found this 3" tall cone roof flashing...
http://www.homedepot.com/p/DuraVent-3-in-Tall-Cone-Pellet-Vent-Roof-Flashing-3PVL-FF/100679720
I could just pull off the existing flashing and old pipe, and use this with a storm collar and some silicone caulk and be done?

 

[jrems]

If it's aluminum, just get an aluminum sheet and form it to the contour of the roof. Make it at least 4" bigger than the hole. Use rivets with backers on the inside. Put a bead of silicone in between and it will sqeeze out as it's rivited together and will be water tight.